Multicell line storms consist of a line of storms with a continuous,
well developed gust front at the leading edge
of the line.
An approaching multicell line
often appears as a dark
bank of clouds covering the western horizon.
The great number of
closely-spaced updraft/downdraft
couplets qualifies this complex as
multicellular, although storm structure
is quite different from that of the
multicell cluster storm.

Multicell line storms are better known as squall lines, which is the
term that we will use from here on. The former name is for positioning squall
lines in the thunderstorm spectrum.

Squall lines most frequently produce severe weather near the
updraft/downdraft interface at the storm's leading edge.
Downburst winds are the
main threat, although hail
as large as golf balls and gustnadoes can occur.
Flash floods
occasionally occur when the squall line decelerates or even
becomes stationary, with thunderstorms moving parallel to the line and
repeatedly across the same area.